Effects of Solids Retention Time on the Anaerobic Membrane Bioreactor with Yttria-Based Ceramic Membrane Treating Domestic Wastewater at Ambient Temperature

Abstract

The effects of solid retention times (SRTs) (100 days, 50 days, 25 days) on the performance, microbial community, and membrane fouling of a lab-scale anaerobic yttria-based ceramic membrane bioreactor (AnCMBR) treating synthetic domestic wastewater at ambient temperature (31.2 ± 2.7 °C) were examined. The soluble chemical oxygen demand (SCOD) removal was higher (89.6%) at 25 days SRT compared with 50 days (39.61%) and 100 days (34.3%) SRT. At 100 days SRT, more Bacteroidetes, Firmicutes, and Proteobacteria were present in the microbial community. At 25 days SRT, more Chloroflexi, Synergistetes, and Pastescibacteria emerged, contributing to the stable performance. The SRT of 25 days has resulted in a more stable microbial community compared with 50 days and 100 days SRT. Both bacterial and archaeal community diversities were higher at 25 days SRT, and the specific production of soluble microbial by-products (SMPs) and extracellular polymeric substances (EPSs) were higher at 25 days SRT as well. Consequently, the membrane flux was lower at 25 days SRT with the increased particle size and the enhanced SMPs and EPSs production. Fourier transform infrared spectroscopy analysis (FTIR) and three-dimensional excitation and emission matrix (3D-EEM) analysis showed that protein and SMPs were the major membrane foulants at all SRT stages. In this study, SRT at 25 days was favorable for the stable operation of an AnCMBR treating domestic wastewater at ambient temperature.

New Insights into the Microbial Diversity of Cake Layer in Yttria Composite Ceramic Tubular Membrane in an Anaerobic Membrane Bioreactor (AnMBR)

“…A continuous stirred tank reactor (CSTR) made of plexiglass with an effective working volume of 15 L was used in this work and it was similar to our previous work [11,12]. The tubular membrane was made of ceramic, Yttria, Zirconia with a nominal pore size of 0.1 µm, and a total area of 0.11 m 2 (HeFei ShiJie Membrane Engineering Co. Ltd., Hefei, China).…”

“…The tubular membrane was made of ceramic, Yttria, Zirconia with a nominal pore size of 0.1 µm, and a total area of 0.11 m 2 (HeFei ShiJie Membrane Engineering Co. Ltd., Hefei, China). A peristaltic pump (BT100-1L, Longer, YZ1515x Pump, Baoding, China) was used to feed synthetic domestic wastewater (The composition is given in our previous work [11] into the reactor and mixed liquor from the reactor was fed in to the external side stream membrane unit using a diaphragm pump (DP-35 diaphragm pump, Xin Xishan industries Co. Ltd., Shanghai, China) and retentate was returned to the reactor while permeate was collected in a tank. The membrane was externally installed allowing inside out filtration.…”

“…The bioreactor was operated at a hydraulic retention time (HRT) of 48 h and three varying solids retention time (SRT) s of 100, 50, 25 days at the ambient temperature. The reactor operational conditions and performance were well discussed in our previous publication [11].Operational transmembrane pressure (TMP) was established at 87 kPa with 54 L/(m 2 •h) as initial and sustainable fluxes. TMP was measured with a pressure transducer and controlled by the valves at the exit of the membrane unit, manually.…”

“…TMP was measured with a pressure transducer and controlled by the valves at the exit of the membrane unit, manually. The schematic diagram of the reactor set up is presented in Figure S1, which was also presented in our previous publications [11,12].…”

“…AnMBR coupled with ceramic membranes (AnCMBR) has been previously studied in numerous studies investigating performance, and fouling, etc. [8][9][10][11][12].…”